Electroencephalogram for Prognosis After Cardiac Arrest

Background: In assessing neurologic prognosis after cardiac arrest (CA), electroencephalogram (EEG) reactivity has not been specifically included with EEG classifications. Most studies have divided recordings into benign and malignant; however, some patterns within these groups may have greater prognostic significance than such broad classifications. We sought to explore reactivity, with broad classifications and subclassifications for their prognostic significance.

Methods: All consecutive adults in coma who had an EEG recording performed at least 1 day after CA or during normothermia after a 24-hour mild hypothermia protocol. Outcomes were dichotomous: recovery of awareness or no recovery of awareness during hospitalization.

Results: Twenty-nine patients met the inclusion criteria. Of the 18 patients with no reactivity, only 1 recovered awareness; of the 11 patients who demonstrated reactivity, 10 recovered awareness (sensitivity of 90% [95% confidence interval, or CI, 0.57-1] and specificity of 94% [95% CI, 0.7-1]). Of those with benign patterns, 7 recovered awareness and 1 did not; however, those patients demonstrating malignant patterns, 4 recovered and 17 did not (sensitivity of 94% [95% CI, 0.7-1] and a specificity of 63% [95% CI, 0.32-0.88]). None of the 15 patients with suppression or generalized spikes recovered consciousness, and none of these patients demonstrated reactivity.

Conclusions: Electroencephalogram reactivity after CA is a relatively favorable EEG feature; generalized suppression or generalized epileptiform activity, without reactivity, is associated with lack of recovery of awareness.